1. Technical Field
The present disclosure relates to a stress sensible screw that can sense instantaneous stress. More particularly, the present disclosure relates to a dust proof structure for the stress-sensible screw. The dust proof structure can prevent dust, oil or moisture from entering an electrical connection portion, thereby reducing an error of the stress signal.
2. Description of Related Art
A screw is a tool widely used for securely screwing two objects together. Concerning public safety issues becomes more and more emphasized, selecting proper screw is very important in the field of precision technology. Also, it is required to perform regular inspections on the stress applied to the screw. For example, a screw having precision stress is essential in the assembly of an air craft, a space ship, a bridge or a steel skeleton reinforced building. Even if the inspections on the stress of the screw pass during the assembly, there is no guarantee on the safety of the screw after the screw suffers surrounding variations, such as metal aging, vibration or metal fatigue.
A kind of stress sensing device has been developed to address the aforementioned issues. In the stress sensing device, a sensor, an operator and a displayer are typically disposed in the screw. However, the build-in sensor, operator and displayer significantly increase the manufacturing cost of a single screw. Furthermore, the displayer is fixed such that the readout of the displayer for torque cannot be viewed in certain angles, which limits the performance of the build-in displayer. Moreover, in case multiple portions need to be sensed, a large amount of high-priced screws is required. When the stress sensing device is applied in a specified environment (e.g. in an aircraft wing), its performance will also be limited concerning the requirements in surrouonding resistance or weight.
In view of the problem, another kind of stress sensing device is commercially available. The stress sensing device utilizes a sensing screw connected to an external displayer. However, in the stress sensing device, a connection portion between the sensing crew and the outer displayer is mostly likely affected by dust, oil or moisture, which changes a contact feature of the connection portion and results in an error of the sensed stress value.